1. Technical Field
The present invention relates to a thin-film transistor and a method for manufacturing the same.
2. Description of Related Art
Display devices typically include thin film transistors and other electronic elements. In these thin film transistors, amorphous silicon are usually used as the material of the semiconductor layers. In recent years, there has been rapid progress in display technologies, and then metal-oxide semiconductor tends to gradually replace the amorphous silicon in the thin film transistors. Among these metal-oxide semiconductor materials, much attention has been given to indium zinc oxide (IGZO) because it possesses a high mobility.
However, the conventional wet etching process exhibits a low etching selectivity between the IGZO semiconductor layer and the source/drain electrodes made of metallic material such as a molybdenum-chromium alloy. Accordingly, the manufacturing process of IGZO thin film transistors is difficult to be satisfactorily controlled
Furthermore, the source/drain electrodes are formed on and in contact with the IGZO semiconductor layer in the conventional IGZO thin film transistors. When a dry etching process is employed to form the source/drain electrodes, ion bombardment possibly damages the back channel of the semiconductor layer, and lead to a degradation of the IGZO semiconductor layer. As a result, the IGZO thin film transistors suffer problems in leakage currents and the shift of threshold voltages after the IGZO thin film transistors are driven for a long time.
Moreover, since the IGZO semiconductor layer is in contact with the metallic source/drain electrodes in conventional IGZO thin film transistors, the effect of the hot-carrier injection possibly becomes serious. Therefore, the mobility of the IGZO layer may be decreased.
In view of the above, there exists in this art a need of an improved IGZG thin film transistor that would resolve the drawbacks mentioned above.